Investigation of Thermal Conductivities and Expansion Coefficients of (Yb_1 − xLa_x)₂AlTaO₇ Ceramics

The (Yb_1 − xLa_x)₂AlTaO₇ (x = 0, 0.1, 0.3, 0.5) ceramics were prepared by solid-state reaction method. The phase composition, microstructure, thermophysical properties of (Yb_1 − xLa_x)₂AlTaO₇ ceramics were investigated. Results reveal that (Yb_1 − xLa_x)₂AlTaO₇ (x = 0, 0.1, 0.3) ceramics exhibit a single pyrochlore-type structure, and the (Yb_0.5La_0.5)₂AlTaO₇ has an orthorhombic weberite structure. The thermal conductivities of (Yb_1 − xLa_x)₂AlTaO₇ (x = 0, 0.1, 0.3) ceramics decrease with increasing Yb₂O₃ contents. (Yb_0.5La_0.5)₂AlTaO₇ has the highest thermal conductivity among all the ceramics studied, within the range of 1.48-1.75 W/m K (20-1200 °C). The thermal expansion coefficients of (Yb_1 − xLa_x)₂AlTaO₇ ceramics decrease gradually with increasing La₂O₃ fractions, and the thermal expansion coefficients are close to those of YSZ.